Such a locking device is known from DE 195 17 728 A1. The lock cylinder is provided with a cylinder sack for receiving the actuator formed as an electric motor. The keyway is open toward the circumferential surface of the cylinder core. The blocking element is formed as a stirrup engaging at its two ends two recesses in the circumferential surface of the cylinder core on either side of the open keyway in the axial area of the cylinder core provided with mechanical tumblers. The actuator formed as an electric motor and disposed in the cylinder sack has a shaft with two opposite cams acting on the stirrup or the cylinder housing in the blocked position.
The known locking device with an electronically and mechanically coded key has proven useful by and large. However, one must replace the total cylinder lock. Also, one can only retrofit cylinder locks with a cylinder sack with this locking device.
DE 42 07 161 A1 discloses a locking device with a lock cylinder wherein an additional electronic lock in the form of an additional cover is provided. The latter contains a cap rotating with the cylinder core.
DE 297 03 063 U1 discloses an additional electromagnetic lock for the cylinder core, said lock engaging recesses on the circumference of the cylinder core.
Further, DE 196 53 113 A1 describes the formation of an annular coil as an antenna for data transmission with a cylinder lock having additional electronic protection.
The problem of the invention is to change over virtually all cylinder locks to such a locking device with electronic, in particular electronic and mechanical, coding without having to replace them.